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California November 4 1999 a nia Department of Transportation , Shop 10 Maintenance Station, Stockton, California Project No 103872-02 sampling activities were transferred into labeled, reconditioned 55-gallon drums The drums were left on-site to be maintained by Caltrans 4.3. Laboratory Analysis The groundwater samples were submitted for analysis to AL, a State of Call fornia-certifled hazardous waste analytical laboratory Samples were analyzed for TPH-G and TPH-D, using method EPA 8015 (modified) Samples were analyzed for BTEX, methyl tertiary-butyl ether (MTBE), tertiary-amyl-methyl ether (TAME), isopropyl ether (DIPE), tertiary butyl (TBA), ethyl-tertiary-butyl ether (ETBE), and volatile organic compounds (VOCs) using method EPA 8260B A summary of the past and present laboratory results for the groundwater sam- ples is presented in Table 1 Copies of laboratory results and chain-of-custody documents are included in Appendix B 5 SUMMARY AND CONCLUSIONS Ninyo & Moore measured depth-to-groundwater and sampled eight wells at the site between September 23 and 24, 1999 Groundwater elevation data indicates that the groundwater flow is to the southeast beneath the site with a Hydraulic gradient of 0 002 feet per foot Comparatively, groundwater measurements recorded during the last monitoring event in June 1999 indicated groundwater movement beneath the site was toward the southeast under a hydraulic gradient of 0 0015 feet per foot The depth to groundwater has increased in all wells since the last sampling event Decreases in groundwater elevations were recorded in wells MW-12 by 2 86 ft , MW-13 by 0 20 ft , MW-14 by 2 80 ft , MW-16 by 0 37 ft , MW-19 by 7 68 ft , NIW-20 W-20by035ft , MW- 24 by 2 47 ft , MW-25 by 0 40 ft , VM-1 by 0 25 ft , and VM-2 by 0 18 ft , respectively Labo- ratory data has indicated increases and decreases in many of the compounds analyzed for in samples taken from various wells on site In well MW-12, Total xylenes increased in concentration from non detect levels to 7 5 micro- gram per liter(µg11) shop 10doc 4